Various assemblies can be installed in a well traversing a hydrocarbon-bearing subterranean formation. During well drilling and completion, a service string can be positioned within a wellbore to perform certain functions. Knowing the position of the service string within the wellbore can reduce damage to the well that can occur if a tool on the service string is activated at the incorrect location within the wellbore. Knowledge of the service string's location within a wellbore is particularly useful in multi-zone wellbores where the service string can be repositioned within various zones. Knowing the location of the service string can help properly position the service string with respect to each zone.